PyQt 的Tree Widget中拖放和点击的异常行为

在 PyQt 的 QTreeWidget 中，如果你遇到拖放和点击的异常行为，可能是由于信号处理、事件拦截、拖放设置或树结构配置等问题导致的。以下是一些可能的常见问题和解决方案。

在这里插入图片描述

1、问题背景

一个 PyQt 应用程序中包含两个 Tree Widget，当用户从一个 Tree Widget 拖动项目并将其释放到另一个 Tree Widget 时，程序运行良好。但是，如果用户将项目拖动并释放到相同的 Tree Widget（这是一种不希望的行为，因此我在代码中禁用了接受拖放操作），Tree Widget 会忽略用户接下来的鼠标点击事件。

当用户拖动一个项目并将其释放到相同的 Tree Widget 时，可以看到以下问题：

用户点击左侧 Tree Widget 中的任何项目，而不会发生任何变化。
用户再次点击相同或其他项目时，选择才会发生改变。
试图点击展开图标，无论用户点击多少次，都不会触发任何事件。

要重现此问题，请运行代码并执行以下步骤：

从左侧的树中拖动一个项目，并将其释放到相同的树中。
单击左侧树中的任何项目，您将注意到没有任何变化
再次单击相同或其他项目，选择就会更改。

2、解决方案

为了解决这个问题，我修改了 MyTreeWidget 的 mousePressEvent 方法，以确保在用户点击 Tree Widget 时鼠标按下位置被正确记录。之前，mousePressEvent 方法只在左键点击时记录鼠标按下位置，这导致了上述异常行为。现在，只要用户点击 Tree Widge，即使没有按下左键，鼠标按下位置都会被记录。

修改后的 mousePressEvent 方法如下：

class MyTreeWidget(QtGui.QTreeWidget):# ...def mousePressEvent(self, event):super(MyTreeWidget, self).mousePressEvent(event)self.mousePressPos = event.pos()

这样可以确保鼠标按下位置始终被正确记录，从而解决了上述异常行为。

完整的代码如下：

from PyQt4 import QtGui, QtCore
import cPickleclass MyTreeItem(QtGui.QTreeWidgetItem):def __init__(self, parent=None):super(MyTreeItem, self).__init__(parent)self.setFlags(QtCore.Qt.ItemIsDragEnabled | QtCore.Qt.ItemIsSelectable | QtCore.Qt.ItemIsUserCheckable | QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsDropEnabled)def getPath(self):"""Rebuild path from the tree."""if isinstance(self.parent(), MyTreeItem):path = '{0}/{1}'.format(self.parent().getPath() ,str(self.text(0)))#The top level itemelse:path = '/{0}'.format(str(self.text(0)))return pathdef getParents(self):"""Get all the parents to the top level."""parents = []while self:self = self.parent()if isinstance(self, MyTreeItem):parents.append(self)return parentsdef getChildren(self):"""Get all the children(flatten)."""children = []if not self:return childrenchildrenCount = self.childCount()if childrenCount == 0:return childrenfor idx in range(childrenCount):citem = self.child(idx)if citem:children.append(citem)children.extend(citem.getChildren())return childrenclass MyTreeWidget(QtGui.QTreeWidget):def __init__(self, parent = None):super(MyTreeWidget, self).__init__(parent)self.setDragEnabled(True)self.setAcceptDrops(True)self.setHeaderLabels(["Select Members"])self.setSelectionMode(QtGui.QAbstractItemView.ExtendedSelection)self.mousePressPos = QtCore.QPoint(0,0)def mousePressEvent(self, event):super(MyTreeWidget, self).mousePressEvent(event)self.mousePressPos = event.pos()def mouseMoveEvent(self, event):super(MyTreeWidget, self).mouseMoveEvent(event)self.setAcceptDrops(False)drag = QtGui.QDrag(self)mime_data = QtCore.QMimeData()passme = []for sel in self.selectedItems():dnddict = {}dnddict['disp'] = sel.getPath()dnddict['val'] = sel.getPath()passme.append(dnddict)bstream = cPickle.dumps(passme)mime_data.setData("application/x-ltreedata", bstream)drag.setMimeData(mime_data)self.setAcceptDrops(True)action = drag.exec_()def mouseReleaseEven(self, event):self.setAcceptDrop(True)event.accept()def dragMoveEvent(self, event):if event.mimeData().hasFormat("application/x-ltreedata"):event.accept()else:event.ignore()def dragEnterEvent(self, event):if event.mimeData().hasFormat("application/x-ltreedata"):event.accept()else:event.ignore()def dropEvent(self, event):if event.source() == self:event.ignore()else:for item in event.source().selectedItems():print item.text(0)def addItems(self, itemList):"""Take a list of path-like strings"""for item in itemList:self.addItem(item)def addItem(self, item):"""Convert each item to a tree item"""joints = item.strip('/').split('/')joint = Nonewhile joints:joint = self.addTreeJoint(joints.pop(0), joint)def addTreeJoint(self, jointName, parent=None):"""Add item to the tree widget"""returnItem = None#If it the top of the treeif not parent:#Find existing itemfor item in self.findItems(QtCore.QString(jointName),QtCore.Qt.MatchExactly):if jointName == item.text(0):return item#Create new top level itemreturnItem = MyTreeItem(self)returnItem.setText(0, jointName)#We search all the children of this tree level and figure out if#we need to create a new tree item.else:for idx in range(parent.childCount()):if parent.childCount() == 0:breakif jointName == parent.child(idx).text(0):return parent.child(idx)#Create new itemreturnItem = MyTreeItem(parent)returnItem.setText(0, jointName)return returnItemclass GeometrySelector(QtGui.QWidget):accepted = QtCore.pyqtSignal(list)def __init__(self, parent = None):super(GeometrySelector, self).__init__(parent)self.treeWidget = MyTreeWidget(self)self.treeWidget.addItems(get_objs())button = QtGui.QPushButton('Add Members', self)button.setFocusPolicy(QtCore.Qt.NoFocus)button.clicked.connect(self.cb_accept)filterLabel = QtGui.QLabel(self)filterLabel.setText('Filter:')filterField = QtGui.QLineEdit(self)filterField.textChanged.connect(self.filterChanged)filterBox = QtGui.QHBoxLayout()filterBox.addWidget(filterLabel)filterBox.addWidget(filterField)mainLayout = QtGui.QGridLayout()mainLayout.addWidget(self.treeWidget,0,0)mainLayout.addLayout(filterBox,1,0)mainLayout.addWidget(button,2,0)self.setLayout(mainLayout)pal = self.palette()pal.setColor(QtGui.QPalette.Base, QtGui.QColor(80, 80, 80))pal.setColor(QtGui.QPalette.Text, QtGui.QColor(230, 230, 230))self.setPalette(pal)button.setPalette(pal)self.treeWidget.setPalette(pal)def filterChanged(self, filterStr):showedItem = []matchFlag = QtCore.Qt.MatchFlags(QtCore.Qt.MatchContains | QtCore.Qt.MatchRecursive | QtCore.Qt.MatchRegExp)allItems = self.treeWidget.findItems(QtCore.